Creating an on-the-fly wireless communications networks is a fundamental element of fire fighting, dealing with hostage situations, and other emergencies. However, it is challenging to assemble such networks without delay and dependably. The National Institute of Standards and Technology (NIST) recently presented details of two experimental networks that tell emergency workers when to set down wireless transmitters to ensure a good signal. These emergency wireless networks could build themselves.
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In a typical scenario, a first
responder equipped with a
two-way radio
and several small relay
nodes enter a building
(Credit: NIST) |
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Ad hoc wireless networks convey messages between transmitters, or nodes, without the need for any central control. However, the current situation forces emergency workers to keep to recommended guidelines for constructing such a wireless network, which dictates laying each node at a distance of 15 or 30 meters and at crucial points, like the corners of buildings. These nodes cyclically report back to a command centre to ensure that the nodes are still in contact.
The newly developed prototype, which took three years to develop, was able to monitor the
signal-to-noise ratio of transmissions, and without human intervention, notify where a new node should be deployed. “We didn’t want to have fixed rules, because there can be a lot of metal in walls or cinder block,” meaning signal strength varies from building to building, says Nader Moayeri, a senior technical advisor in NIST’s
Advanced Network Technologies Division. “Plus, you don’t want to deploy too many, because of the cost factor as well as potential for communication delays.”
Moayeri also adds that during the brainstorming process two alternatives for the
NIST algorithm surfaced. The first method was to enable nodes to ping each other with short messages and calculate the number of packets of data that were lost in transit. However, the problem with this technique was that if there were any weak or lost signals, then the whole system would need to retrace its steps. This might result in a loss of resources and valuable time. To overcome this issue, a second scheme was designed to compute the signal-to-noise ratio and offer a robust idea of the intensity of the connection.
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| 2.4 GHz prototype relay node (Credit: NIST) |
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Utilizing off-the-shelf hardware, the team built two prototype networks. One uses a Crossbow MICA2 Motes, which transmits radio signals at 900 megahertz, and the other, using Linux-based Gumstix transmitters, a Wi-Fi network that operates at 2.4 gigahertz. The speciality of this algorithm is that it should be able to work with any wireless hardware and on any available spectrum and has the potential to improve considerably emergency force readiness.
Additional information on the new ad-hoc algorithm can be obtained at NIST
website.
